Extra fluids may be fatal

Anyone with a cold knows they should drink plenty of fluids to get better more quickly.

But the advice given by nearly all doctors is probably wrong and may actually cause serious harm, especially to children, it is claimed today.

Research suggests that drinking more than you need when the body is tackling an infection could lead to "fluid overload". This may eventually affect the brain, causing fits and even death, according to Professor Chris Del Mar.

He said: "The best advice we should be giving patients is to drink when thirsty. Patients are often told to drink plenty of fluids when they're suffering colds and flu but there is indirect evidence this could be harmful.

"In particular, children are likely to be encouraged to drink more by worried parents.

"But you can have too much of a good thing - and excess amounts of fluid can affect the body's natural mechanism for conserving fluids during an infection."

Adults can expect to suffer between two and five colds a year. GPs normally advise patients to keep warm and take plenty of fluids to avoid dehydration. But Prof Del Mar, professor of general practice at Queensland University, Australia, and colleagues examined trials into the effects of giving increased fluids to patients with respiratory infections.

Fluids could be potentially harmful

He found little evidence to support the practice but "indirect" evidence from experiments that it could be potentially harmful, says a report in the British Medical Journal.

During a respiratory infection such as a cold, flu or bronchitis, the body releases large amounts of a water-conserving substance known as antidiuretic hormone.

It is possible that giving excess fluid while this happens may lead to salt loss and fluid overload, said Prof Del Mar.

In one study of children with pneumonia - none of whom were dehydrated - four children who died were found to have very low salt levels.

He said: "The body is designed to conserve fluids when fighting infection in case it is not possible for the patient to drink.

"As a result, taking in too much fluid can upset the balance the body is trying to maintain. It can result in the brain becoming waterlogged, leading to lethargy, irritability, fits, coma and even death."

The lack of evidence showing that drinking extra fluids is helpful came as a surprise to the research team, he said, adding: "We always thought the advice was self-evident and justfiied on the basis that even if the benefit is uncertain, or at best small, at least it is harmless.

"We need to be more cautious about universally recommending increased fluids to patients, especially when they feel they don't need it.

"It is best to be guided by your thirst, drink when you feel your body needs it rather than taking in a lot of fluid just because that's the advice doctors have always given," he added.

Doctors concerned

However, London GP Dr Chaand Nagpaul said last night that he would be concerned if parents tried to withhold fluids from their children as a result of the research.

He said: "The research shows a theoretical, indirect risk of providing too much fluid but in my experience this is not what happens in practice.

"Most parents have to coax their children to drink when they are ill with respiratory infections, or have fever, diarrhoea or vomiting, because they don't want to.

"But there is a very real risk of dehydration with this type of illness and it is essential to ensure children get sufficient fluids to remain hydrated and prevent them gettng sicker.

"I would be very concerned if parents did not take the sensible view that their children must be encouraged to drink when they are ill.

"I think doctors will continue to advise patients that it's important to keep up a reasonable intake of fluids."